tcg/tci: fix logic error when registering helpers via FFI

tcg/tci: fix logic error when registering helpers via FFI

When registering helpers via FFI for TCI, the inner loop that iterates
parameters of the helper reuses (and thus pollutes) the same variable
used by the outer loop that iterates all helpers, thus made some helpers
unregistered.

Fix this logic error by using a dedicated temporary variable for the
inner loop.

Fixes: 22f15579fa ("tcg: Build ffi data structures for helpers")
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Icenowy Zheng <uwu@icenowy.me>
Message-Id: <20221028072145.1593205-1-uwu@icenowy.me>
[rth: Move declaration of j to the for loop itself]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>